Dual battery charging generator system

ABSTRACT

A battery charging generator which is capable of charging two series connected batteries in a motor vehicle electrical system where the series connected batteries are used to energize the cranking motor of a motor vehicle. The generator is of the alternating current type and has first and second three-phase full-wave bridge rectifier units built into the end frame of the generator each of which is capable of supplying charging current to one of the batteries. The generator has a built-in transistor voltage regulator which senses the voltage applied to the main battery of the system by the first bridge rectifier and which regulates the output voltage of the generator to a predetermined value. The second bridge rectifier supplies charging current to an auxiliary battery and is connected with the stator winding of the alternating current generator by means of a three-phase transformer. The transformer, like the bridge rectifiers, is built into the end frame of the generator and isolates the two bridge rectifiers of the system. The generator is arranged with a 12 volt and a 24 volt output terminal which only need be connected directly to the batteries when installing a generator on a motor vehicle.

This application is a division of copending application Ser. No.406,701, filed on Oct. 15, 1973 and now U.S. Pat. No. 3,863,127.

This invention relates to a battery charging generator and moreparticularly to a single unit diode-rectified alternating currentgenerator which is capable of developing two direct voltage outputswhich are utilized to charge a pair of storage batteries.

The motor vehicle electrical systems of certain vehicles such as largeover the highway trucks, utilize a 24 volt cranking motor to crank theengine. In order to charge the batteries of such a system and to provideproper cranking motor voltage, it has been common practice to use aseries-parallel switch in conjunction with a battery charging generatorand a cranking motor. The series-parallel switch connects two 12 voltbatteries in parallel and across the charging generator when it isdesired to charge the batteries and connects the batteries in series toprovide 24 volts for energizing the cranking motor when it is desired tocrank the engine.

In order to eliminate the series-parallel switch it has been proposed toarrange a system where a conductor maintains a series connection betweenthe batteries, such that the cranking motor can be energized whenever aswitch connects the series connected batteries and the cranking motor.In order to charge the batteries, systems of this type have employed anauxiliary circuit for charging one of the batteries. An example of thistype of system is disclosed in the U.S. Pat. to Huntzinger et al., No.3,671,843 in which one of the batteries is charged from a converterwhich has a rectified output that is used to charge the battery.

In contrast to the systems that have been described, the presentinvention contemplates providing a single-unit diode-rectifiedalternating current generator which is provided with direct currentoutput terminals that can be utilized to respectively charge twoseries-connected 12 volt batteries that are capable of energizing a 24volt cranking motor. The battery charging generator of this inventionrather than utilizing auxiliary external apparatus uses the three phaseoutput winding of the generator to charge both batteries. Thealternating current generator has a frame which supports a pair of threephase full-wave bridge rectifier units. One of the bridge rectifierunits has its A.C. input terminals connected directly with thethree-phase output winding of the generator and this bridge rectifierunit has direct current output terminals which are utilized to chargethe battery that supplies the normal electrical loads on the vehicle.The other three-phase full-wave bridge rectifier unit is connected tothe three-phase output winding of the generator through a three-phasetransformer which is also built into the end frame of the generator. Thetransformer has a substantially 1:1 turns ratio and effectively isolatesthe two bridge rectifiers. The second bridge rectifier has directcurrent output terminals which are utilized to charge the auxiliary 12volt battery for the electrical system.

It accordingly, is one of the objects of this invention to provide asingle unit diode-rectified alternating current generator which hasdirect current output terminals that can be connected with twoseries-connected storage batteries to provide charging current for thestorage batteries and wherein the system includes a built-in transformerfor isolating the two rectifier units from each other.

Another object of this invention is to provide a dual battery charginggenerator of the type described where the generator has a built-intransistor voltage regulator which senses the direct voltage output ofthe bridge rectifier that supplies charging current to the main batteryof the system that supplies the normal electrical loads on the motorvehicle and wherein the system operates such that this regulator alsocontrols the output voltage of the rectifier that supplies chargingcurrent to the auxiliary battery.

Still another object of this invention is to provide a dual voltagediode-rectified alternating current generator wherein a pair of bridgerectifier units are built into the end frame of the generator andwherein the bridge rectifier units are substantially aligned with eachother so as to provide a compact unit that is easily electricallyconnected with both the stator winding of the generator and atransformer which feeds the bridge rectifier unit that is used to chargethe auxiliary battery.

Another object of this invention is to provide a dual battery chargingsystem of the type described wherein the turns ratio of the transformeris of such a value as to aid in preventing overcharging of the auxiliarybattery during operation of the system.

IN THE DRAWINGS

FIG. 1 is a sectional view of a dual voltage diode rectified alternatingcurrent generator made in accordance with this invention;

FIG. 2 is an end view of the generator shown in FIG. 1 looking in thedirection of the arrows 2--2 of FIG. 1;

FIG. 3 is a view of the generator shown in FIG. 1 taken along lines 3--3of FIG. 1;

FIG. 4 is a view of the generator shown in FIG. 1 taken along lines 4--4of FIG. 1; and

FIG. 5 is a schematic circuit diagram of the complete electrical systemof the diode-rectified alternating current generator of this invention.

Referring now to the drawings and more particularly to FIG. 1, thereference numeral 10 designates the end frame of the battery charginggenerator made in accordance with this invention. This end frame isformed of a metallic material such as die cast aluminum. The end frame10 is generally tubular and has air outlet openings designated byreference numeral 12. The generator of FIG. 1 has another substantiallytubular end frame designated by reference numeral 14 which may also beformed of aluminum material. The end frames 10 and 14 are securedtogether by a plurality of through bolts, one of which is shown in FIG.1 and designated by reference numeral 16. The end frames 10 and 14support a stator assembly generally designated by reference numeral 18.The stator assembly 18 includes a core 20 formed of magnetic materialhaving an annular portion 20A which is clamped between end frames 10 and14. The annular core 20 has the usual stator slots and these slots carrya three phase delta-connected stator winding designated by referencenumeral 22 and shown schematically in FIG. 5. In FIG. 5 the phasewindings of the stator or output windings of the generators have beendesignated by reference numerals 22A, 22B and 22C.

The frame parts 10 and 14 rotatably support a rotor for the alternatingcurrent generator which is generally designated by reference numeral 23.The rotor assembly 23 includes a shaft 24 which is supported in bearings26 and 28 that in turn are supported by parts of the frames 10 and 14.The shaft 24 has a splined section 30 which carries an annular coremember designated by reference numeral 32 that is formed of magneticmaterial. The core part 32 drives a rotor segment or pole memberdesignated by reference numeral 34. The rotor segment 34 has a pluralityof circumferentially spaced axially extending teeth 34A which areinterleaved with the teeth of another rotor segment designated byreference numeral 36. The segments 34 and 36 are connected together byan annular non-magnetic part designated by reference numeral 38 which isriveted or otherwise secured to the segments and the arrangement is suchthat the pole or segment 34 drives the part 36 through the non-magneticpart 38. The two rotor segments form a well-known Lundell type of rotorof the same type as disclosed in the U.S. Pat. to Raver No. 3,271,601.

The rotor segments 34 and 36 rotate about an annular field coil assemblygenerally designated by reference numeral 40. This field coil assemblyincludes the field coil 42 and a core member formed of magnetic materialdesignated by reference numeral 46. The core member 46 is supported by apart of the end frame 14 and is secured thereto by fasteners 47.

The alternating current generator as has been thus far described, is thewell-known brushless Lundell type disclosed in the U.S. Pat. to RaverNo. 3,271,601. Thus, when the field coil 42 is energized with directcurrent and when the rotor segments 34 and 36 are rotated relative tothe stator assembly 18 and the fixed coil assembly 40, an alternatingcurrent is generated in the delta-connected stator winding 22.

The particular form of the alternating current generator forms no partof this invention and this generator can take various configurations aslong as an alternating current is generated in the stator winding 22 asthe shaft is driven.

Attached to the open end of the frame or housing 14 is a metallichousing designated by reference numeral 50. The housing 50 has a flangesection 52 formed with a plurality of openings 54 which receive bolts 56for securing the housing 50 to the frame part 14. The bolts 56 arethreaded into threaded openings 58 formed in the housing 14. Thethreaded openings 58 are formed in the flat end walls 59 and portions 61of the frame 14 as can be seen in FIG. 3. The flange section 52 ofhousing 50 mounts flat against end walls 59 and portions 61 when housing50 is secured to frame 14. It can be seen from FIG. 3 that the end walls59 and portions 61 do not form a continuous wall for engaging flangesection 52. Thus, at a plurality of areas designated by referencenumeral 63 the frame 14 is axially spaced from flange section 52 ofhousing 50 to form air inlet openings for the generator.

The housing or frame 14 contains a three-phase fullwave bridge rectifierassembly which is generally designated by reference numeral 70. Thisbridge rectifier assembly as is best illustrated in FIG. 3, is comprisedof a pair of finned aluminum heat sinks designated by reference numeral70A and 70B. The heat sink 70A carries three silicon diodes which arenot illustrated. These diodes have their cathodes electrically connectedto the heat sink 70A and these diodes are designated by referencenumeral 72 in the schematic circuit diagram of FIG. 5. The heat sink 70Blikewise carries three silicon diodes which are not illustrated in FIG.3 but which are identified by reference numeral 74 in FIG. 5. The heatsinks 70A and 70B are secured to each other by a suitable insulatingmaterial designated in its entirety by reference numeral 76. The bridgerectifier assembly 70 has three A.C. input terminals designatedrespectively by reference numeral 78. These A.C. input terminals arethreaded terminals supported by the insulating material of the rectifierassembly and each A.C. input terminal is connected respectively with theanode and cathode of a respective silicon diode 72 and 74. The diodes ofbridge rectifier assembly 70 can be supported in a manner disclosed inthe U.S. Pat. Nos. to Christman et al., 3,697,814 or Cheetham et al.,3,538,362.

It will be appreciated by those skilled in the art that the bridgerectifier unit 70 comprises two finned aluminum heat sinks which areelectrically insulated from each other and which each carry threesilicon diodes forming a three-phase full-wave bridge rectifier unit.The positive and negative direct current output terminals of the bridgerectifier unit are respectively the heat sinks 70A and 70B and theseheat sinks have been identified in the same manner in the circuitdiagram of FIG. 5.

The bridge rectifier unit 70 is secured to the interior of the frame 14by the screws or bolts 80 which pass through the slots formed in heatsink 70B and which are threaded into suitable openings formed in bossesin an interior wall of frame 14. The heat sink 70B is electricallyconnected to the frame 14 and therefore is at ground potential as isindicated in the schematic circuit diagram of FIG. 5.

The heat sink 70A has a threaded opening which receives a screwdesignated by reference numeral 83. The screw 83 serves to electricallyconnect apertured spade connectors on conductors 84 and 86 with the heatsink 70A and these conductors are therefore at the positive potential ofthe bridge rectifier 70. The conductor 84 is connected to one side ofcapacitor 86. The opposite side of the capacitor 86 is supported by theframe 14 and therefore is at ground potential as is illustrated in FIG.5.

The conductor 86 is electrically connected with a terminal studdesignated by reference numeral 90. The terminal stud 90 passes througha suitable opening formed in the wall portion 92 of the housing 14. Thestud 90 is electrically insulated from the housing 14 and forms one ofthe direct current output terminals for the charging generator of thisinvention. As seen in FIG. 5, the terminal stud 90 is utilized to supplycharging current to one of the batteries in the dual battery system. Thedirect voltage appearing between terminal stud 90 and ground, as willbecome more readily apparent hereinafter, is used for charging the main12 volt battery of the electrical system.

The housing 14 in addition to containing the bridge rectifier unit 70contains a voltage regulator which is generally designated by referencenumeral 94. The voltage regulator is of a transistor type and itsphysical construction can be the same as that disclosed in the U.S. Pat.to Cheetham et al., No. 3,538,362. The voltage regulator 94 is securedto a heat-sink section 96 of frame 14 by a plurality of screwsdesignated by reference numeral 98 that pass through openings formed inthe voltage regulator 94 and which are threaded into the portion 96 offrame 14. The openings in the regulator 94 are circumscribed by annularelectrical connectors for the regulator as disclosed in the abovementioned Cheetham et al. patent.

It can be seen from the schematic circuit diagram of FIG. 5 that thejunction 100 of the voltage regulator 94 is connected with a conductor102 which is also illustrated in FIG. 3. The conductor 102 is actually astrip of metallic material connected to the cathodes of three diodes104. One end of conductor 102 has an opening that receives one of thescrews 98. The diodes 104 are contained within a housing designated byreference numeral 106 in FIG. 3. The diodes are connected with aperturedconductors 108 illustrated in FIGS. 3 and 5 which are slipped over theterminals 78 that form the A.C. input terminals of the bridge rectifierunit 70. The diodes 104 therefore are contained in a suitable housingwhich has conductors 108 extending therefrom and these diodes areconnected as shown in FIG. 5.

The junction or terminal 100 of voltage regulator 94 is connected withanother conductor which is designated by reference numeral 110 in theschematic circuit diagram of FIG. 5. This connection is made by anapertured connector connected to conductor 110 that receives a screw 98.The conductor 110 is shown in FIG. 3 and this conductor is connected toone side of the field winding 42 of the alternating current generator.The opposite side of the field coil 42 is connected with a conductor 112which in turn is connected to a junction 114 of the voltage regulator 94by a connector receiving a mounting screw 98. Both conductors 110 and112 are illustrated in FIG. 3, it being understood that they passthrough the frame 14 and are electrically connected to opposite ends ofthe field coil 42.

The voltage regulator 94 has another terminal designated by referencenumeral 116. The terminal 116 is electrically connected to the positiveside of the bridge rectifier 70A by a conductor 118 which is illustratedin the schematic circuit diagram of FIG. 5 and also in FIG. 3. As seenin FIG. 3, the conductor 118 is connected to an apertured terminal clip120 which in turn is fixed and electrically connected to the heat sink70A by a screw 123 that is threaded into heat sink 70A.

The voltage regulator 94 can be of various circuit configurations one ofwhich is illustrated in FIG. 5. As seen in FIG. 5, the regulator is ofthe transistor type and comprises a pair of NPN transistors 126 and 128.The transistors 126 and 128 are connected in the known Darlingtonconfiguration and the collector-emitter circuit of transistor 126 isconnected between one side of the field winding 42 and ground. The fieldwinding 42 is shunted by a field discharge diode 130. A resistor 131 isconnected between junction 100 and the base of transistor 128. Thevoltage regulator 94 further includes a driver transistor designated byreference numeral 132. The driver transistor 132 has its emitterconnected to ground at conductor 134 and has its collector connectedwith resistor 136. The opposite side of resistor 136 is connected withjunction 116. The base of transistor 132 is connected to a junction 138.A capacitor 140 is connected between junction 138 and ground. Thejunction 138 is connected with a Zener diode 142 which is connected inseries with a resistor 144. The opposite side of resistor 144 isconnected with a junction 146 located between voltage dividing resistors148 and 150. A resistor 152 is connected between junction 116 and theresistor 148 and has been illustrated in FIG. 5 as a variable resistor.In a preferred form, the variable resistance 152 is provided by avoltage adjusting arrangement of the type which is disclosed in the U.S.Pat. to Alexander et al., No. 3,659,188. Thus, as shown in that patent,the projecting terminals of the voltage regulator 94 (not illustrated)are fitted with an insulated connector which is designated by referencenumeral 154 in FIG. 3. The connector 154 fits within an opening formedin the frame 14 and is adapted to receive a voltage adjustment cubeformed of a plurality of resistors of the type illustrated in the abovementioned Alexander et al. patent and not disclosed herein. This voltageadjustment feature forms no part of the present invention and can takeother forms if so desired.

Referring now to FIG. 3, it is seen that the input terminal studs 78 ofthe bridge rectifier 70 are electrically connected with apertured spadeconnectors connected to conductors 160. The conductors 160 asillustrated in FIGS. 1 and 5, are electrically connected to the statorwinding 22 of the alternating current generator. It can be seen fromFIG. 3 that the conductors pass through a slitted rubber grommet 162located between heat sink 70A and an inner wall of the housing 14. Allof the connector terminals that are slipped on terminals 78 are held inplace by nuts illustrated in FIG. 3.

The housing 50 which is secured to housing 14 carries a three-phasedelta-connected transformer generally designated by reference numeral170 in FIG. 5. The transformer 170 (FIG. 4) includes a core formed ofmagnetic material having end sections 170A and 170B and three legs 172which carry the coil windings 174. The coil windings 174 include theprimary and secondary phase windings of the transformer and in theschematic circuit diagram of FIG. 5 the primary phase windings have beendesignated by reference numeral 174A whereas the secondary phasewindings are designated by reference numeral 174B. It is to beunderstood that the primary and secondary windings are wound on therespective legs 172 of the core of the transformer as shown in FIG. 4.The magnetic core member of the transformer 174 is bolted to the innerwall of the housing 50 by suitable screws or fasteners designated byreference numeral 176 that are threaded into housing 50. It can be seenfrom the schematic circuit diagram of FIG. 5 that the primary windings174A of the transformer 170 are connected with the A.C. input terminals78 of bridge rectifier 70 and they are therefore electrically connectedto the stator winding 22 of the generator. The physical connection ofthe primary windings 174A with the terminal studs 78 is made throughconductors designated in their entirety by reference numeral 178 andillustrated in FIG. 4. The terminal connectors on conductors 178 havenot been illustrated but it is understood that the connectors haveopenings receiving studs 78 and are connected thereto. From theforegoing, it can be seen that the primary windings of the transformer170 are delta-connected to the A.C. input terminals 78 of the bridgerectifier 70 by way of conductors 178 extending from the lower side ofthe transformer 170 up to the terminals 78.

Disposed within the housing 50 is another three-phase full-wave bridgerectifier unit generally designated by reference numeral 180 which isbest illustrated in FIG. 4. The bridge rectifier unit 180 is like thatshown in the above mentioned U.S. Pat. to Christman et al., No.3,697,814. Thus, the bridge rectifier unit 180 comprises finned aluminumheat sinks 180A and 180B as illustrated in FIG. 4. These aluminum heatsinks are supported and insulated from each other by insulating materialgenerally designated by reference numeral 182. The heat sink 180A asshown schematically in FIG. 5, forms the negative direct current outputterminal for the bridge rectifier unit 180. The heat sink 180A carriesthree silicon diodes designated by reference numeral 181 in FIG. 5 whichhave their anodes connected to the heat sink 180A in a manner disclosedin the above mentioned Christman et al. patent. In a similar manner, theheat sink 180B carries three silicon diodes 182 which have theircathodes electrically connected to the heat sink 180B. The heat sink180B forms the positive output terminal for the bridge rectifier unit180 while the heat sink 180A forms the negative direct current outputterminal for the bridge rectifier 180. The negative terminal or heatsink 180A is electrically connected with a conductor 184 (FIG. 4) by ascrew 185 passing through a connector on conductor 184 and through amounting slot formed in heat sink 180A. The screw 185 is threaded intohousing 50 and is insulated from heat sink 180A. The opposite end ofconductor 184 is electrically connected with the heat sink 70A byapertured terminal 121 connected to conductor 184 and held in place byscrew 123 (see FIG. 3). It thus is seen that the conductor 184 serves todirectly electrically connect the heat sink 180A of bridge rectifierunit 180 with the heat sink 70A of bridge rectifier unit 70. This isalso illustrated in the schematic circuit diagram of FIG. 5.

The positive heat sink 180B of bridge rectifier unit 180 is electricallyconnected with a terminal stud 190 by a conductor 192. The conductor 192is attached to an apertured terminal 192A which receives a screw 192Bthat passes through an opening in heat sink 180B. The screw 192B isthreaded into the housing 50 and with screw 185 serves to secure therectifier unit 180 to housing 50. The rectifier unit 180 is insulatedfrom the frame 50 by insulation including insulator 192C. The terminalstud 190 extends through one side wall of the housing 50 and iselectrically insulated from the housing. The terminal stud 190 isillustrated as a terminal in the schematic circuit diagram of FIG. 5.

The bridge rectifier unit 180 has three threaded terminal studsdesignated by reference numeral 194 connected to diodes 181 and 182 in amanner shown in the above mentioned Christman et al. patent. Theseterminal studs 194 form A.C. input terminals for the unit 180. Theterminal studs 194 as shown in FIGS. 4 and 5 are connected with thesecondary windings 174B of the transformer 170 by conductors which havebeen designated by reference numeral 196. The conductors have the usualterminals fitted on studs 194 which are held in place by nuts 195. Theconnections are such as can be seen from FIGS. 4 and 5, that a conductorfrom a respective secondary winding 174B is commonly connected to one ofthe terminal studs 194 of the bridge rectifier unit 180.

Referring now to FIG. 3, it is seen that the housing 14 carries aterminal designated by reference numeral 206 connected to conductor 208.The conductor 208 in turn is connected with one of the terminal studs 78and the terminal 206 provides a relay terminal for the generator whichmay be utilized to energize a relay or other electrical apparatusbetween A.C. input terminal 78 and ground.

The generator of this invention is air cooled and to this end a fan 209is secured to the shaft 32 and is driven thereby. The fan 209 draws airout of the openings 12 formed in the end frame 10 and causes air to bepulled into the generator through the air inlet openings mentionedbefore. The shipping tube 210 is shown secured to the generator shaft 30but it is to be understood that when the generator is installed in amotor vehicle a suitable pulley, not illustrated, will be secured to theshaft 24 to drive the shaft. The pulley is, of course, belt driven bythe engine of the motor vehicle.

The operation of the dual voltage generator of this invention will nowbe described. In the use of the generator of this invention thegenerator is suitably supported by mounting brackets on the motorvehicle by bolts that pass through the openings formed in the bushings212. The pulley of the generator, which is not illustrated, as mentionedhereinbefore, is belt driven by the engine of the motor vehicle.

The primary purpose of the generator of this invention, as has beendescribed, is to provide two direct voltage outputs that are suitablefor charging two equal terminal voltage storage batteries found on themotor vehicle. It will be evident from the circuit diagram of FIG. 5that the output terminal 90 will provide a direct voltage between it andground which is the proper voltage to charge the 12 volt storage batterydesignated by reference numeral 214 in FIG. 5. The storage battery 214is the battery that is utilized on the motor vehicle to supply thenormal electrical loads such as the headlights, accessories, etc., andthese electrical loads have been designated by reference numeral 216. Aconductor 218 connects the output terminal 90 to the positive side ofbattery 214 at junction 220. The conductor 218 also serves to supply thenormal electrical loads on the vehicle whenever switch 222 is closed.

The other 12 volt storage battery is designated by reference numeral 224and this battery is only used when it is desired to energize thecranking motor 227 for cranking the engine of the motor vehicle. Thepositive side of battery 224 is connected to the output terminal 190 ofthe generator by a conductor 226. The positive side of the storagebattery 224 can be electrically connected to the cranking motor 226whenever starter switch 228 is closed through conductor 230. It can beseen from FIG. 5 that the batteries 214 and 224 are connected in seriesby conductor 221 and that no switching device is required toelectrically connect these batteries in series when it is desired toenergize the cranking motor 226. It will also be appreciated that theauxiliary battery 224 is charged from a circuit that can be traced fromoutput terminal 190, through conductor 226, through battery 224, throughconductor 218 to heat sink 70A and then through conductor 184 to heatsink 180A which forms the negative terminal for the bridge rectifier180.

In operation of this system, the voltage regulator 94 senses the voltageappearing between heat sink 70A and ground via conductor 118. Thisvoltage is divided by resistors 152, 148 and 150 so that a voltageappears at junction 146 which is a function of the output voltage ofbridge rectifier 70. Where the battery 214 is a 12 volt battery, thecharging voltage for the battery is maintained at some voltage higherthan this and the voltage regulator 94 performs this function. Thus, asthe output voltage of the bridge rectifier 70 exceeds the desiredregulated value, Zener diode 142 breaks down causing the transistor 132to be forward biased. This causes the potential of the collector oftransistor 132 to approach ground potential with the effect thattransistors 126 and 128 are turned off. This reduces the output voltageof the generator 70 to a value such that the transistor 132 is biasedoff with the result that transistors 126 and 128 are biased on. Theswitching of transistors 126 and 128 between on and off conditionsregulates the current flow through the field winding 42 such that adesired regulated voltage is developed by the alternating currentgenerator and rectified by the rectifier 70 to charge battery 214 and tosupply the electrical loads 216 on the motor vehicle.

As mentioned before, the turns ratio of the transformer 170 issubstantially 1:1. However, in order to prevent overcharging the battery224 it is preferred that the transformer slightly step-down the voltagebetween primary and secondary. Thus, it has been found that a turnsratio of 42 turns per primary phase to 41 turns per secondary phase or astep-down ratio of 42 to 41 provides a good charging characteristic forbattery 224. This means that the charging voltage applied to battery 224will be slightly less than the same voltage that is applied to battery214 from the bridge rectifier 70 since the A.C. input voltage to thebridge rectifier 180 is slightly less (by a ratio of 41/42) than themagnitude of A.C. input voltage to the bridge rectifier 70. It thereforecan be seen that the voltage regulator regulates the output voltage ofthe system by sensing the output voltage of bridge rectifier 70 but inso doing the output voltage of bridge rectifier 180 is also regulated toprovide a proper charging voltage for the battery 224.

It will be appreciated by those skilled in the art that the transformer170 serves to isolate the bridge rectifiers 70 and 180 from each other.If no transformer were provided it would be necessary to provide aswitch to maintain the two charging circuits for the batteries 214 and224 disconnected during battery charging. Thus, were the A.C. inputterminals of the bridge rectifiers 70 and 180 both directly connected tothe generator output winding 22, instead of a transformer connectionbridge rectifier 180, the A.C. output windings of the generator would beshorted through a pair of series-connected diodes, one from each bridgerectifier during operation. This could be remedied by a circuitarrangement where conductor 70A is not connected to conductor 218 butrather is connected to the positive side of battery 214 by a separateconductor. This supposed circuit arrangement would require a switchconnected between junction 220 and the point at which 70A is connectedto the positive side of battery 214 by the separate conductor. Thisswitch would be open during battery charging and closed during enginecranking. The transformer connection of this invention eliminates thisswitch and its associated wiring by preventing any shorting of generatorwinding 22.

In summary, it will be appreciated that the generator of this inventionprovides two direct output voltages for charging two batteries which areconnected in series and which can be utilized to energize a crankingmotor. Since all the components of the system are built into thegenerator it is only necessary to electrically connect the outputterminals 190 and 90 to the batteries when it is desired to use thegenerator on a motor vehicle. It will be further appreciated that thegenerator of this invention completely eliminates a series-parallelswitch or any other type of switch contactors for selectively connectingthe batteries in parallel during charging and in series for energizingthe cranking motor.

It will be appreciated by those skilled in the art that the frame partsof the generator of this invention are grounded and when the generatoris supported in the vehicle a ground connection is made. If desired,however, the generator may be electrically connected to ground by agrounding strap which is connected to a grounding screw designated byreference numeral 234 which is threaded into a suitable threaded openingformed in the frame part 14.

The slitted rubber grommet 162, that receives conductors 160, is wedgedbetween an inner wall of housing 14 and heat sink part 70A. This grommetserves to electrically insulate part 70A from housing 14, serves as anupper support for heat sink assembly 70 and also serves to supportconductors 160.

The particular construction of bridge rectifier units 70 and 180 couldtake known forms other than the ones specifically disclosed herein aslong as they are capable of being used as a part of the overall systemdisclosed herein.

What is claimed is:
 1. An electrical system associated with an internalcombustion engine comprising, a load battery having a predeterminedvoltage rating, a second auxiliary battery of like voltage rating,first, second and third terminals, means connecting said load batterybetween said first and second terminals, means connecting said auxiliarybattery between said second and third terminals, a cranking motorcircuit connected across said first and third terminals, an electricalload circuit connected across said first and second terminals, apolyphase alternating current generator having a polyphase outputwinding and a field winding, a polyphase rectifier having A.C. inputterminals and two direct voltage output terminals, means connecting saidinput terminals of said polyphase rectifier to said output winding, saidpolyphase rectifier operable to rectify the polyphase output voltagegenerated in said output winding into a direct voltage appearing acrossthe direct voltage output terminals of said polyphase rectifier, meansconnecting said two direct voltage output terminals of said polyphaserectifier respectively to said first and second terminals, a voltageregulator connected to sense the voltage across said load battery andacross said direct voltage output terminals of said polyphase rectifierfor controlling the energization of said field winding to therebymaintain the voltage across said load battery at a desired regulatedvalue, an isolation transformer having primary and secondary windings,means connecting said primary winding of said isolation transformer tosaid output winding, a second rectifier having input terminals and twooutput terminals, means connecting said secondary winding of saidisolation transformer to said input terminals of said second rectifier,means connecting said two ouutput terminals of said second rectifier tosaid second and third terminals, the turns ratio of said isolationtransformer being such as to produce an open circuit average voltage atthe output of said second rectifier substantially equal to 0.97 of theopen circuit average voltage at the output of said polyphase rectifier.2. An electrical system for charging a pair of series-connectedbatteries that are adapted to energize an electrical cranking motorcircuit comprising, a first load battery, a second auxiliary battery oflike voltage rating, first, second and third terminal means, meansconnecting said first load battery between said first and secondterminal means, means connecting said auxiliary battery between saidsecond and third terminal means whereby said batteries are connected inseries additive relationship between said first and third terminalmeans, said first and third terminal means being adapted to supply acranking motor circuit at a voltage equal to the series-additivevoltages of said batteries, an alternating current generator having athree phase output winding and a field winding, a first three phasefullwave bridge rectifier having A.C. input terminals and direct voltageoutput terminals, means connecting said A.C. input terminals of saidfirst bridge rectifier to said three phase output winding of saidgenerator, means connecting said direct voltage output terminals of saidfirst bridge rectifier with said first and second terminal means wherebysaid first load battery is charged thereby, a three phase transformerhaving primary and secondary windings, a second three phase full-wavebridge rectifier having A.C. input terminals and direct voltage outputterminals, means connecting said primary winding of said transformer tosaid output winding, means connecting said secondary winding of saidtransformer to said A.C. input terminals of said second bridgerectifier, means connecting the direct voltage output terminals of saidsecond bridge rectifier across said second and third terminal meanswhereby said second auxiliary battery is charged thereby, and a voltageregulator connected to said field winding and with the direct voltageoutput terminals of said first bridge rectifier, said voltage regulatorcontrolling field current to control the magnitude of the voltagegenerated in said output winding to provide a desired regulated voltageat the output of said first bridge rectifier and across said first loadbattery in response to the voltage applied to said first load batteryfrom the direct voltage output terminals of said first bridge rectifier,the ratio of secondary turns to primary turns of said transformer beingsubstantially equal to 0.97 to thereby step-down the transformer inputvoltage.